This invention relates to a graft copolymer emulsion and a waterborne polymer composition containing the graft copolymer emulsion, the emulsion comprising a polymer backbone and a macromonomer compound. This composition is stabilized anionically and contains 0.5 to 30 weight percent of an amine-functional monomer copolymerized in the backbone and/or the macromonomer. The copolymer emulsions of this invention can be cured with a polyisocyanate.
Coating compositions generally comprise a carrier liquid, a film-forming polymer and a curing (crosslinking) agent. For waterborne coatings, the carrier liquid is primarily water. The combination of the film-forming polymer and the crosslinking agent is commonly referred to as a binder. It is desirable that the binder have a low viscosity such that the binder is readily sprayable using automated spraying equipment and a high solids content such that an adequate paint film thickness is yielded with one to two cross-passes of a spray gun.
In a one-package system, the binder is contained within a single package, and curing is typically accomplished by baking the coating after application. In a two-package (2K) system, the binder is contained in two separate packages: a first package contains the film-forming polymer and a second package contains the curing agent. Shortly prior to application, the contents of the two packages are combined, and curing occurs through chemical crosslinking reactions. Once the two packages are combined, the crosslinking reaction is irreversible, and thus two-package systems have a relatively short pot life.
Film-forming polymers most commonly employed are linear addition-type copolymers containing functional groups such as hydroxyl groups, and these copolymers are cured by reaction with crosslinking agents. In two-package urethane technology, curing agents based on isocyanate functional polymers are used that, upon mixing with a hydroxy-functional copolymer, react to form a crosslinked network.
The most relevant art appears to be WO95/32229. This publication, however, does not disclose the particular graft copolymer emulsion (of this invention) or the coating composition (of this invention) characterized as they are by the combination of excellent dry-film build, Persoz hardness, and solvent-resistance described herein (see Table 11).